The overall goal of this program project proposal is to elucidate the signaling and transcriptional pathways involved in specifying unique functions of sub-populations of vascular smooth muscle and endothelial cells. Recent molecular data confirms prior clinical observations that different parts of the vasculature are inherently distinct. For instance, pulmonary vascular smooth muscle and arterial smooth muscle react differently to disease states and pharmacological intervention. Even within the arterial tree, smooth muscle arises from distinct precursors variably affecting congenital vascular disorders. Vascular and lymphatic endothelial cells are specified in such a way as to express distinct molecular markers and adopt divergent functions. Despite these observations, little is known about how these distinctions are orchestrated or how they contribute to functional differences within the vasculature. The over-riding hypothesis guiding this program is that vascular heterogeneity is established by a series of local, region-specific, non cell-autonomous pathways that involve secreted signaling molecules and cell-cell interactions. We plan to examine this hypothesis by pursuing 4 collaborative projects that examine region-specific examples of smooth muscle and endothelial differentiation throughout the vasculature. These include: 1) Diverse origins of vascular smooth muscle and relationship to congenital cardiovascular disease; 2) Wnt signaling and lung vascular development (Morrisey); 3) The function of myocardin in vascular smooth muscle cells; 4) Molecular regulation of blood-lymphatic endothelial differentiation. These projects will be supported by an Administrative Core, and by Core facilities for Histology and Gene Expression and Transgenic and Knockout Mice. This revised application responds to the suggestions of the prior review and is more focused and interactive. Initiatives that met with the least enthusiasm have been eliminated while other areas have been strengthened with additional data, collaborators and experimental approaches. The overlapping approaches and techniques used in this program will be relevant for understanding congenital and acquired vascular disease and for development of interventions that target specific populations of vascular cells.